A jet-propulsion personal watercraft for use in leisure, sport, etc., is equipped with an engine in an interior of a body including a hull and a deck covering the hull from above. An exhaust gas emitted from the engine is exhausted outside the body, through an exhaust system that is equipped behind the engine in the interior of the body and is configured to reduce the energy of the exhaust gas. As disclosed in Japanese Laid-Open Patent Application Publication No. 2004-98966 (in particular FIG. 3) and Japanese Laid-Open Patent Application Publication No. Hei. 9-236015, some personal watercraft include two mufflers arranged on right and left sides to accommodate an exhaust system in a limited inner space of a relatively small body.
In the exhaust system disclosed in Japanese Laid-Open Patent Application Publication No. 2004-98966, cylindrical mufflers each having closed both ends are positioned on an upstream side and on a downstream side in a flow of an exhaust gas and are arranged on right and left sides of the body. The exhaust gas emitted from an engine flows into the upstream muffler and then into a front portion of the downstream muffler through a first exhaust pipe extending from a rear portion of the upstream muffler. Further, the exhaust gas is discharged outside the body through a second exhaust pipe extending from a rear portion of the downstream muffler and through a region behind the first exhaust pipe. Thus, the exhaust system including the upstream muffler and the downstream muffler is efficiently disposed in the limited inner space of the body. In addition, the exhaust gas is repeatedly expanded and contracted while flowing through the upstream muffler, the first exhaust pipe, the downstream muffler, and the second exhaust pipe, in this order. As a result, the energy of the exhaust gas is efficiently reduced.
The center of gravity of a personal watercraft is a factor in determining a running characteristic of the personal watercraft, and therefore flexibility in positioning of the center of gravity is desirable. Because the center of gravity of the personal watercraft is substantially affected by the location of the engine, which is the component having the largest weight, there is a need for flexibility in the placement of the engine. Personal watercraft are typically equipped with an article accommodating compartment in a front part of the body. The engine is desirably positioned rearward rather than forward to increase a volume of the article accommodating portion.